A motion detector of the prior art is described e.g. in DE 197 25 806 A1. The motion detector described in this document is a revolution detector in which the moving element is a rotor having at least two sectors of differing magnetic properties. The signal processing circuit in this known revolution detector consists of an RC pad which generates a dc signal from each train of oscillating signals produced when the oscillating circuit is pulse activated. The level of the dc signal continues to violate an input threshold of a microprocessor serving as the analyzer as long as the amplitudes of the oscillations violate a critical threshold value. Such a revolution detector may be employed, e.g. in consumption meters, e.g. in water meters.
One drawback of the signal processing circuit employed hitherto is that it is relatively complicated and thus cost-intensive, it being the capacitor used therein that is particularly the cause of this. Another drawback is that the time constant of the RC pad containing the capacitor alters with aging of the capacitor which in the worst case may even result in circuit failure. In addition to this, due to the relatively high time constants of the RC pad only low sampling rates are possible.